I have a shapefile containing network of rivers for the whole country. The description of the layer is saying that orientation of the vector should be the same as the river flow. This is true for most of the lines, but not for all of them.

I would like to find the vector with the wrong orientation and change it. I have already found a way with python how to change direction.

The problem is selecting all the broken elements: dataset is big(more then 300 000 elements), so that it was I cannot do it manually and looking for automatic solution.